1. Technical Field
Example embodiments of the present invention relate in general to a technology for cancelling interference in a wireless communication system, and more specifically, to a method of cancelling inter-subcarrier interference in distributed antenna system, which can efficiently cancel inter-subcarrier interference in distributed antenna system using Alamouti coded orthogonal frequency division multiplexing (OFDM).
2. Related Art
According to rapid advances of wireless communication system, demands on transmitting and receiving a high-speed large amount of data are increasing. For this, a method of installing a plurality of distributed antennas additionally in the conventional cell coverage, and performing cooperative communications between a plurality of transmitters and a plurality of receivers, which are geographically distributed, is being used.
Such the distributed antenna system has an effect of resolving a problem of coverage hole, decreasing transmission power, and enhancing transmission efficiency per bandwidth, and especially a system which makes use of relay nodes connected to a base station through optic cables as distributed antenna has a strong point in high-efficient resource allocation and a cooperative signal transmission between distributed antennas, since the system does not require additional radio resources for relaying and transmission/reception of control signals.
Meanwhile, since circuits processing a large number of subcarriers may be implemented on a single integrated circuit according to advances of semi-conductor technology, it has become possible to convert high-speed data into low-speed parallel data and transmit the converted low-speed parallel data. In addition, since computation has become more simplified according to adopting a Fast Fourier Transform (FFT) signal processing, an Orthogonal Frequency Division Multiplexing (OFDM) is being applied to various commercial wireless or mobile telecommunication systems.
Also, recently, an Alamouti coded OFDM, which obtains transmit antenna gains by using Alamouti codes in distributed antenna system, is being used. In the distributed antenna system, in order to maximize diversity gain, interferences due to frequency errors are required to be reduced.
In a wireless communication system using a time-space code based Alamouti coded OFDM, in order to cancel interferences due to frequency errors between transmit antennas, a conventional method of transferring information on drifts generated due to the frequency error from a receiving part to a transmitting part has been used. Thus, the conventional method has shortcoming of increasing signaling overhead.
Also, since N-point Inverse Fast Fourier Transform (IFFT)/Fast Fourier Transform (FFT) computations have been used conventionally, there has been a problem that effects of residual interference components are large even after cancelling inter-subcarrier interferences, and a method of transmitting null data for resolving the problem has been used. However, the method of transmitting null data has a shortcoming in decreasing a data transmission rate.